The present invention relates to a surgical instrument assembly for use in endoscopic surgery, particularly endoscopic neurosurgery.
Surgical instrument assemblies for use with rigid or flexible endoscopes are well known in biopsy procedures and certain types of endosurgery. A telescope portion of the endoscope is generally housed within a sleeve which also houses the shaft of a single surgical instrument. The sleeve and surgical instrument each has a proximal end and a distal end. The distal end of the surgical instrument is an operative end having an operative function. The operative end of the surgical instrument protrudes from the distal sleeve end into a field of view of the endoscope, and is controllable from the proximal end by the surgeon. Such assemblies have been widely used in relatively simple procedures where lateral to and fro manipulation of the operative end of the surgical instrument within the field of view is not required.
Systems permitting manipulation of a flexible distal end portion of a surgical instrument (e.g. a catheter or flexible surgical tool) in one lateral to and fro direction within the field of view are also known. Thus, for example, U.S. Pat. No. 2,038,394 (Wappler) describes a catheterising cystoscope, having the facility to deflect the distal end of a catheter inserted into a body cavity, within a field of view of an endoscope. British Patent Application No. 2004749 describes a modification of such a system, in which a proximal operating lever is provided to control a deflector at the distal end, which lever may be manipulated by the fingers of the hand used for holding the assembly. Furthermore, the operating mechanism of the lever is spring-loaded to cause return of the lever (and return of the deflector) when the finger pressure is released. In this way, the lateral to and fro manipulation of the flexible end portion of the surgical instrument is accomplished by the surgeon using one finger of one hand to manipulate the operating lever. The surgeon can thus use the same hand for adjusting the angular position of the deflector, while using the other hand to advance, twist or withdraw the instrument.
Such unifunctional instrument assemblies have found use in neurosurgery and other relatively complex procedures, including aspiration of intracerebral hematomas, drainage of chronic subdural hematomas, the fenestration of arachnoid and other cysts, third ventriculostomy, choroid plexus fulguration and spinal disc exenteration. In some of these systems a second or subsequent surgical instrument may be introduced down a parallel sleeve, but the systems lack the means for concerted interaction between surgical instruments.
Neuroendoscopic surgery shows a wealth of potential as a neurosurgical technique, which has hitherto been substantially unrealised due to a lack of appropriate surgical equipment. Unlike other current trends in computer-assisted point targeting systems, neuroendoscopy is primarily an optical system in the tradition of macro- and microsurgery. The great hope for endoscopy is its ability to provide for a minimal approach. Parallel function, with instrument systems which operate independently of the endoscopic position, can allow for a confined approach, with a reduction in unnecessary lateral dissection and retraction. This is enhanced by the greater ease with which paraxial areas can be seen, and with flexible endoscope systems more peripheral areas could also be visualized from within the same minimal approach. Endoscopy also enables stability in the operating system and instruments, in contradistinction to microsurgery, where the stability of the instruments is directly dependent upon the surgeon and his or her ability to operate in an awkward postural position, which in turn is subservient to the optimal position of the microscope. With endoscopy the use of television monitors from which to operate can give the surgeon enormous postural freedom and freedom of movement, with the instruments held at a convenient distance from the body. With the added stability imparted to the instruments by the endoscopic system, it is likely that neuroendoscopy is easier to master than microsurgery.
A particular advantage of endoscopy is that it is depth independent. With the optical viewing point at, or around, the tissue-instrument interface regardless of the depth, this means that the same viewing quality is maintained throughout. Endoscopy can provide a really excellent view of the tissue and instruments; if the optical telescope function is made independent of the parent endoscope as will be discussed in greater detail below, a variety of viewing perspectives could be easily attained, without altering the overall intracranial position of the parent endoscope.
In International (PCT) Patent Application No. WO 92/19146 there is described (FIGS. 10 and 11) a laser instrument for use in neuroendoscopic and similar delicate procedures, having an ergonomic handle to provide specific control. The instrument comprises a thin rigid hollow shaft carrying an internal laser fibre and having a distal end provided with a deflector for the fibre and a proximal end to which is pivotally attached the ergonomic control handle. The handle is hollow and internally carries the laser fibre, apart from one portion of the fibre which lies exposed against the outside of the handle. Fine control of advancement/retraction of the laser fibre is provided by simple index finger pressure by the surgeon on the exposed portion of the fibre to press it against the handle. The handle is connected to the deflector via a push-pull wire pair passing through the hollow shaft and arranged so that pivotal movement of the handle causes the deflector to move to deflect the operative end of the laser fibre. The instrument is mounted with an endoscope telescope in an instrument assembly during use. Generally similar instruments are also described, in which the distal end has a mechanically operable function (e.g. a bipolar diathermy tool, a rongeurs tool or a forceps tool) and the handle is provided with a rocker mechanism operated by the surgeon""s index and middle fingers to control the operation of the instruments.
The ergonomic handle of the instruments described in WO 92/19146 is an elongate handle of a xe2x80x9cpencil gripxe2x80x9d type. It suffers from three prime disadvantages. Firstly, the use of the rocker mechanism for controlling mechanically operable distal end parts makes it difficult for the surgeon to grip the handle securely without fear of inadvertently moving the distal end of the instrument. Secondly, the handle of the laser instrument, which in contrast to the other instruments described can be securely gripped between the surgeon""s thumb and middle finger, is attached to laser generating apparatus and the surgeon cannot move his or her hand around the end of the handle while maintaining a secure grip between the thumb and middle finger. Thirdly, the pivoting of the handle to control the instrument deflection function requires an inconvenient wrist movement by the surgeon.
It is an object of the present invention to provide an improved or at least alternative surgical instrument assembly for use in endoscopic surgery, particularly endoscopic neurosurgery.
According to a first aspect of the present invention, there is provided a surgical instrument assembly for use in endoscopic surgery, particularly endoscopic neurosurgery, the assembly comprising:
(a) a surgical instrument having proximal manually operable instrument control means and distal operative means coupled thereto, the operative and control means being spaced mutually apart by a shaft, and a handle being provided in general proximity to the control means whereby a surgeon can hold the instrument;
(b) optical means (more particularly an endoscope telescope and lighting system) for viewing a distal end of the instrument in an operating zone within a patient; and
(c) support means for retaining the instrument and optical viewing means in use so as to present the distal end of the instrument for viewing in the operating zone within the patient and to present the control means externally of the patient for manipulation by the surgeon;
characterised in that: the handle is ergonomically configured as a generally elongate handle provided with surface depressions arranged to accommodate at least a thumb tip and middle finger tip of the surgeon whereby the surgeon can grip fast the handle substantially directly between thumb and middle finger; and
the handle extends no more than about 5 cm beyond the point of grip and the instrument is adapted to permit the surgeon to rotate his/her hand around the handle in unrestricted movement while maintaining the grip between thumb and middle finger.
The handle is preferably mounted fast to the instrument, i.e. without any pivotal movement between handle and instrument, and most preferably extends at right angles to the longitudinal direction of the shaft. The handle and control means are conveniently releasably mounted to the shaft as a removable, reusable, unit as will be discussed in greater detail below. The unit is most preferably sterilisable (e.g. autoclavable) for reuse and constructed from lightweight materials to minimise hand fatigue and maximise responsiveness. Metals such as aluminium or titanium are mentioned as particularly suitable. Synthetic materials such as lightweight resins may also be used.
The handle may if desired be hollow, to minimise its weight. In this case, it is preferred that the handle is formed as a releasable pair of handle halves, to allow all interior surfaces to be effectively sterilised for reuse.
The surface depressions for the surgeon""s thumb tip and middle finger are suitably provided at approximately the midpoint along the length of the handle. Further surface depressions are preferably provided in the handle to accommodate the surgeon""s index and/or fourth finger tips. Each depression is preferably approximately 2 to 8 mm, e.g. about 5 mm, deep and approximately 10 to 30 mm, e.g. about 15 to 20 mm, long.
The instrument control means are provided in general proximity to the handle. More particularly, it is preferred that the instrument control means are arranged to be operable by the surgeon""s index and/or fourth finger without releasing the grip on the handle between the thumb and middle finger. For this purpose, the instrument control means may suitably comprise one or more triggers, levers, wheels or similar actuating members operatively coupled to the distal operative means of the instrument. The actuating member(s) is/are preferably spaced from, but close to, the surface depression provided in the handle for the surgeon""s index and/or fourth finger tip, whereby the surgeon can simply extend his or her index or fourth finger away from the handle to operate the desired actuating member, and subsequently return the finger to rest on the handle.
The number of actuating members is determined by the functionality of the instrument. The instruments of prime utility in delicate endoscopic surgical procedures all have at least a distal deflection function, whereby the distal end of the instrument can be moved laterally to and fro within the field of view. In such instruments the primary operative means is the distal end deflection system. In addition, instruments may have secondary and further functions, each of which will have their own associated distal operative means, each of which in turn may either be coupled to their own proximal manually operable instrument control means or to alternative instrument control means such as pedal or other remote controls.
Thus, for example, suction instruments, dissection forceps, laser fibre applicators, non-crushing grasping forceps, biopsy rongeurs, scissors, arachnoid dissectors and bipolar diathermy instruments may all be used; the primary operative means is a distal end deflector system, with in some cases secondary distal operative means actuating jaws, blades, cusps etc. Possible additional functionality may include heating (diathermy).
The handle preferably performs no direct instrument control function itself; however, in an alternative embodiment an adjacent trigger or lever instrument actuating member can be conformed so that, when brought fast to the handle on full actuation of the instrument function concerned, that actuating member and the handle together constitute a handle for the instrument according to the first aspect of the invention.
Operative coupling of the proximal manually operable instrument control means to the distal operative means of the instrument may be accomplished via a push-pull mechanical linkage of the type generally described in PCT Patent Application No. Wo 92/19146 (the disclosure of which is incorporated herein by reference). However, such coupling imposes a minimum size on the shaft and distal end of the instrument, which is undesirably large for neurosurgery, where instruments of diameter of approximately 2 mm are ideally required. Accordingly, it is preferred that the operative coupling is effected by means of longitudinally slidable parts associated with or comprising the shaft of the instrument and bearing against elastic or resilient operative portions at the distal end of the shaft. Alternatively, but less preferably, hydraulic and/or pneumatic coupling may be used.
The use of longitudinally slidable parts associated with or comprising the shaft of a surgical instrument, to effect operative coupling of proximal manually operable instrument control means thereof and distal operative means thereof, is new per se, and constitutes a second aspect of the present invention, irrespective of whether or not such instruments are used in a surgical instrument assembly according to the first aspect of the invention.
In more detail, the preferred operative coupling system in the case of a unifunctional instrument for which only a primary distal deflection function is required under the surgeon""s manual control comprises a generally firm but pliant outer tube constituting an outer sheath part of the shaft of the instrument, an operative inner part of the shaft of the instrument lying within the tube and the distal end of the operative inner part of the instrument projecting from a distal end of the outer tube and angulated away from the axis of the instrument at or near the point of exit from the distal end of the tube. The instrument control means are preferably arranged so that on movement of the actuating member by the surgeon""s finger a longitudinal relative sliding movement is mechanically imparted between the operative inner part of the instrument and the outer tube causing the distal end of the tube to overlie the angulated portion, which thereby causes the distal end of the instrument to straighten. The deflection is preferably induced against the restoring force of resilient means (e.g. a spring) associated with the actuating member, so that the instrument returns to its resting condition on release of the surgeon""s finger pressure.
The operative inner part of the shaft of the instrument may, for example, be a suction tube or a laser fibre. The operative inner part of the shaft of the instrument is preferably anchored to the handle portion of the instrument, with the outer sheath part of the shaft movable in the desired relative sliding motion.
In the case of a multifunctional instrument, the single tube is replaced by a coaxial pair of slidable tubes one housed within the other. The distal end of the inner tube projects from the distal end of the outer tube and is angulated away from the axis of the instrument analogously to the instrument lying within the inner tube. As before, the operative inner part of the shaft of the instrument is preferably anchored to the handle portion of the instrument, with the pair of tubes being movable in the desired relative sliding motion. The distal deflection function is analogous to that described for a unifunctional instrument, save that the inner tube is also straightened by the relative movement of the inner and outer tubes. The operative inner part of the shaft of the instrument, lying within the tube pair, suitably comprises control parts for secondary operative means projecting from the distal end of the inner tube. Such control parts may, for example, be anchoring limbs for operative distal jaws, blades or cusps, which anchor the operative means to the handle to permit said relative sliding movement of the overlying tube parts.
The secondary function, which may for example be closing/opening of the secondary operative means such as jaws, blades or cusps projecting from the distal end of the inner tube, is achieved by arranging the instrument control means so that, on movement of the relevant actuating member by the surgeon""s finger a longitudinal relative sliding movement is mechanically imparted between the operative inner part of the shaft of the instrument and the inner tube (but not between the operative inner part of the shaft of the instrument and the outer tube).
By arranging the operative inner part of the shaft of the instrument and the inner tube so that the inner tube constitutes a yoke overlying secondary operative means control parts of the instrument which are arranged to move in response to sliding movement of the yoke and thereby to actuate the secondary operative means of the instrument, the said longitudinal relative sliding movement between the control parts and the inner tube causes the distal secondary operative means of the instrument to be actuated. In a manner analogous to the unifunctional system, the relevant actuating member for the secondary function is associated with resilient means (e.g. a spring) which provides a restoring force returning the instrument to its resting condition on release of the surgeon""s finger pressure. Moreover, by constructing the secondary operative means control parts of the instrument from a resilient material such as elastic metal, and arranging that the yoke-induced movement of those parts is against the resilient restoring force the control parts will similarly return to their resting condition, causing the secondary operative means of the instrument to correspondingly return to their resting condition on release of the surgeon""s finger pressure.
The actuating systems described above enable a variety of surgical instruments to be constructed for use in endoscopic surgery, at far smaller diameters than conventional lever (mechanical) based mechanisms currently permit.
The optical viewing Means is particularly an endoscopic telescope, which may be a flexible or rigid optical system of conventional construction. The surgeon may wish to use one of a range of telescopes depending on the requirements of the surgical procedure. For example, it can be useful sometimes to use a flexible mini-endoscope, or at other times rigid telescopes having different angled field collecting lenses. The optical viewing means will be used in conjunction with lighting systems of generally conventional construction (e.g. fibre optic illumination of the field of view). However, it is preferred that, in the instrument assembly of the present invention, the lighting system is not integral with the optical viewing means, and that the two are movable independently of each other. In this way, an endoscope telescope, for example, can be advanced/retracted or otherwise moved independently of a fibre optic bundle and in conjunction and synchrony with the instruments, as will be discussed in greater detail below.
A stereoscopic endoscopic telescope should preferably be used, although this is not essential. Such a system requires a double viewing system equivalent to two parallel telescopes, and the resultant increased size may be inconvenient in some surgical procedures.
The telescope is suitably linked in conventional manner to a closed-circuit video camera system, which is preferably integral with the assembly.
Alternatively, a flexible endoscope such as a flexible mini-endoscope can be used as the main telescopic system. Steerable flexible endoscopes are preferred, but in this event means must be provided for locking the endoscopic telescope in position. Such a steerable endoscope typically incorporates three push-pull wires attached to a short distal rigid section containing the field collecting lens system, the wires being used to deflect the rigid section in any desired direction.
Forward oblique endoscope telescopes are generally preferred, having a maximum of about 30xc2x0 field collecting lens to reduce distortion during close-up viewing.
The telescope may suitably be connected to a closed-circuit video camera for ease of visualisation. It is preferred that a novel design of telescope lens is employed with the assembly of the present invention, as will be described in greater detail below.
The support means for retaining the instrument and optical viewing means in use must be capable of securely anchoring any optical telescope as any accidental movement of such a heavy piece of equipment in a neurosurgical operating zone can be fatal to the patient. This risk is especially acute when a closed-circuit video camera or other viewing or lighting equipment is mounted to the telescope. The anchoring will preferably be releasable, as one of the advantages of the assembly of the invention will be that the optical viewing system can be rotated and adjusted to alter the surgeon""s field of view. The support system is of generally conventional construction known for rigid endoscopes and is preferably securely mounted to an operating table so that accidental movement with respect to the patient is impossible.
Most preferably, the support means comprises a rigid shaft having a plurality of parallel through channels extending along its length. A large slip-ring arrangement will suitably be provided in conventional manner, linked to a non-damaging (e.g. rubber) wheel projecting into the through channel for the telescope, to allow for the advance/retraction mechanism for the telescope. Rotation of the slip-ring by the surgeon""s finger will cause slow advancement/retraction of the telescope via the rotation of the rubber wheel against the telescope.
In use the shaft extends into the operating zone and is securely anchored at the proximal end, typically via an easy-release fixation system of conventional arm construction used for endoscopes. The fixation system is attached to a detachable side handle provided on the shaft, which handle in turn is used for convenient positioning of both shaft and fixation system. When used properly these systems provide a stable operating platform from which to manipulate the instrumentation. The fixation system is preferably used to anchor the endoscope to the operating table or other support.
The lighting system is preferably a fibre optic bundle packed into all available space between the various channels of the shaft of the support means.
Fixation may also be effected via a stereotactic frame. Stereotaxy limits movement, but facilitates anatomical accuracy in applicable situations and is therefore preferred by some surgeons.
The fixation system should be distally attached to the operating table. It may alternatively be anchored to the skull in adults, but this alternative has been found to be less satisfactory, especially with the additional weight of a CCD camera. Free-standing systems are able to support this weight, but unless heavy and stable, are potentially lethal if knocked. Skull based fixation systems cannot be used in children, and are not practical for supporting weight. Table mounted systems are therefore the most satisfactory.
In use, the shaft of the support means preferably lies horizontal. The shaft should have an outer diameter of no more than about 6 mm. The optical channel, for housing the endoscopic telescope, suitably occupies the upper position in the shaft. The one or more working channels for housing the instrument(s) are suitably beneath the optical channel. It is preferred that two working channels are present, suitably of a design generally compatible with all instruments, so that the surgeon can operate bimanually with two instruments simultaneously.
Beneath the level of the working channels there is provided a passive fluid escape channel to allow drainage of fluid and debris from out of the operating zone. The passive fluid escape channel is connected proximally to a drainage tube providing gravity drainage and collection of all fluids.
Two small further irrigation channels are suitably further provided in the shaft of the support means, preferably either side of the optical channel, to enable a continuous flow of clear fluid across the field-collecting lens of the telescope, to remove debris from the field of view. Conventional control and fail-safe mechanisms are also provided to ensure that when irrigation fluid is used the intracranial pressure does not rise unduly. Neuroendoscopy requires constant irrigation and this is particularly crucial in the presence of bleeding or debris. A pressure and volume monitoring system of conventional construction is preferred for this purpose. The hydrostatic pressure of the irrigation fluid should be the minimum pressure under which passive fluid escape will still be satisfactorily accomplished via the passive fluid escape channel. The hydrostatic pressure should suitably be the lesser of 15 cm (H2O) or L cm(H2O) (where L is the length of the shaft of the support means).
The channels will carry no teats, taps or stops, as these are inappropriate in neurosurgical systems where any tendency to build up intracranial fluid pressure must be avoided It is also desirable to avoid the necessity of direct transcerebral routes wherever possible and to adopt subarachnoid cisternal approaches to lesions within the head. This requires the use of compliant, responsive instrument systems, which can easily be manipulated at a distance from the immediate position of the parent endoscope.
The support means provides stability to the instrument system. The instrument shaft can thus be stabilized within the fixed working channel, so facilitating precise and delicate movement of the instrument working tip. This is readily achieved within a rigid endoscopic system. With flexible systems the proximal end of the flexible endoscope should also be stabilised via a fixation system, and the distal end easily xe2x80x9clockedxe2x80x9d in position to increase stability and facilitate bimanual instrument function. By using CCD cameras and operating from high-definition monitors, the surgeon does not have to adopt awkward operating postures of body or hands as one sees in microneurosurgery. This renders endosurgery easier to perform than microsurgery.
The provision of a lighting system (e.g. fibre optic bundle) as mentioned above, which is of fixed location relative to the support means and does not move with the endoscope telescope, provides substantial advantages to endoscopic surgical instruments in general, irrespective of whether or not they are present in an instrument assembly according to the present invention.
According to a further aspect of the present invention, therefore, there is provided a surgical instrument assembly for use in endoscopic surgery, particularly endoscopic neurosurgery, the assembly comprising:
(a) a surgical instrument having proximal manually operable instrument control means and distal operative means coupled thereto, the operative and control means being spaced mutually apart by a shaft, and a handle in general proximity to the control means whereby a surgeon can hold the instrument;
(b) optical means comprising an endoscope telescope and lighting system, for viewing a distal end of the instrument in an operating zone within a patient; and
(c) support means for retaining the instrument and optical viewing means in use so as to present the distal end of the instrument for viewing in the operating zone within the patient and to present the control means externally of the patient for manipulation by the surgeon;
characterised in that: the lighting system is independent of the endoscope telescope and is of fixed location relative to the support means to illuminate a predetermined region of the operating zone relative to the support means;
the instrument shaft is retained by the support means in an orientation generally parallel to, but offset from, the endoscope telescope; and
the endoscope telescope is movable in conjunction with the surgical instrument relative to the support means and lighting system.
The parts (a), (b) and (c) are preferably as described above in relation to the first aspect of the invention.
The lighting system is preferably generally concentric with the support means, for maximum illumination of the central operating zone.
By offsetting the axes of the instrument and the telescope a side view of the distal end of the instrument can advantageously be gained in the operating zone within the patient.
The above arrangement allows the telescope to be adjusted independently of the position of the support means and in conjunction with the instrument (s). The distal end of the telescope can therefore be maintained generally at an optimum separation from the distal operative means of the instrument(s), having regard to the image distortion found particularly with close or distant spacing of objects from the distal end of the telescope. The support means can then be fixed at a single advantageous position relative to the operating zone and not moved, while both the instrument(s) and telescope can be moved in concert. The telescope can be retracted into the support means and the exact entry point of the instrument(s) into the operating zone seen and controlled towards their target area(s).
During surgery the surgeon should be seated comfortably, with the support means of the instrument assembly of the present invention positioned horizontally. The instruments are introduced beneath the level of the optical telescope system (rigid lens or flexible system) and thereby enter the surgical field under direct vision for maximal safety. Thereafter manipulation of the instruments occurs in three planes, rotation around their long axis, advance/withdrawal into and out of the surgical field, and lateral movement distally by means of controlled deflection within the surgical field. Advance and withdrawal is simply effected, with rotation controlled by the novel instrument handles as defined. These should be set at 90xc2x0 to the main shaft and allow 180xc2x0 of rotation through the hand, when principally held between the thumb and third finger. This should be capable of being effected without ever needing to release the principal grip on the instruments. Primary and secondary function is preferably effected via a spring-trigger or analogous action, using the index finger, or alternatively the fourth finger depending on the disposition of the hand.
Furthermore, the optical viewing system can also be moved during the surgical procedure. Thus, the surgeon can move from an overview (for monitoring the status of neighbouring areas, e.g. any bleeding or inadvertent damage, and equally for orientation of the surgeon""s position and progress along a particular approach) to a close-up view of a target area during an operation. In neuroendoscopy it is important to be able to perform this change without altering the position of the support shaft. Independent synchronized function allows the instruments to be followed throughout their trajectory without altering the position of the support shaft, and therefore minimizing damage to adjacent structures.
A particular difficulty with known endoscopic systems lies in the fact that the fibre optic bundles often become fouled with debris, brain tissue or blood, which reduces visibility and is difficult to correct without withdrawing the endoscope for cleaning, before re-introduction and commensurate increase in tissue trauma. Furthermore, light from such optical bundles is poorly focused within the operating zone. Delicate endbscopic surgical procedures require high quality lighting and optimal visibility at all times which known systems cannot adequately provide.
According to a further aspect of the present invention, therefore, there is provided a fibre optic light guide for illuminating an operating zone for endoscopic surgery (particularly endoscopic neurosurgery) within a patient, the light guide comprising elongate light-conveying optical fibres or fibre bundles having a distal end for illuminating the operating zone and contiguous at their distal end with a distinct smooth protective and physiologically benign, transparent, refractive lens providing a convex end surface (e.g. of glass or other suitably transparent refractive material) whereby the conveyed light is focused onto the operating zone and the optic fibres are not injured or fouled by tissue (especially brain tissue, debris or blood). Optimal visibility can thus be readily maintained under normal conditions.
The novel light guide is preferably used as the lighting system in the various aspects of the invention previously described. Where this lighting system is of fixed location relative to the support means of a surgical instrument assembly, the fibres or fibre bundles preferably lie within the support means so that the distal end of the fibres or fibre bundles corresponds to the distal end of the support means and the convex end surface of the lens overlying the fibres or fibre bundles is preferably at least partially, preferably substantially completely, contained within the diameter of the support means. In this way the lens width and its focusing effect are maximised while still keeping the light guide within the overall dimensions of the support means.
Where the support means takes the form of a shaft carrying a plurality of through-channels, corresponding channels are provided through the portion of the light guide which overlies the distal end of the shaft. Removable channel occluders are preferably also used to temporarily close the channels and reconstitute a perfect curved surface for the convex end surface during introduction of the assembly into the patient, to prevent tissue or fluids from fouling the channels.